Might be best to identify the type of seacock you have. If it is a Blakes you may be able to loosen off the nuts that hold the tension on the cock and then apply pressure to the handle. If its a gate valve you can pull it apart but be aware the water will rush in at some force. If its a ball valve some can be pulled apart but best not on a mooring. What ever you do, avoid using too much force and have your tapered wooden plug handy.

Not sure why you need to shut the valve to sort out no water flow. If the valve is blocked disconnecting the water pipe above the waterline and back flushing may help. No water flow out the exhaust is most likely a worn impeller or a worn impeller face or even a broken shaft. I would suggest checking the water pump first.

Looks like a plastic ball valve. Not sure why its even on the engine. I presumed we were talking about hull seacock to the engine. What's on the other end of that rubber hose? Should have a valve at the skin fitting to shut off the water flow. If that hose comes from just a skin fitting with no valve then removing that clip and pulling off the hose and quickly replacing with a correctly sized bung and reclamp will enable you to service the valve.
CAUTION; depending how far below the waterline that valve is, water will enter at a startling speed! I used to regularly pull off a 2 inch hose to clear and I can assure you it comes through at some force.

That funny cylinder sounds like a heat exchanger. The anode could have disappeared and salts blocked all the spaces or tubes where the cooling water flows. The end should be able to be removed and the tubes rodded out. It could also be an oil cooler. Try posting a photo showing the whole unit.

Impellers in water pumps will last only a couple of minutes if run dry. I would be checking the state of the impeller first. If the water is going past the water pump then the heat exchanger is probably the culprit for the blockage. Underneath the heat exchanger there will be a cast iron section of pipe where the hot exhaust gases mix with the usually cool seawater, a Y section. This is a sacrificial section that blocks up. Pull off the heavy hose and poke a screw driver up the hole. This regularly blocks up with engines that are not run hard enough, running at idle or fast idle with no load for an hour or so charging batteries for example!

That funny cylinder is just an intake with multiple screw fittings for fitting other stuff.

Could it be a blockage at the inlet.does water come in if you loosen the cover on the basket filter.abuild up of antifouling and a little growth greatly reduced water flow on my boat

doug27 said..

Could it be a blockage at the inlet.does water come in if you loosen the cover on the basket filter.abuild up of antifouling and a little growth greatly reduced water flow on my boat

doug27 said..

Could it be a blockage at the inlet.does water come in if you loosen the cover on the basket filter.abuild up of antifouling and a little growth greatly reduced water flow on my boat

nswsailor said..

Not good, not good at all.

We had a yacht leave Camden Haven a couple of years ago and he got the bar all wrong on the way out.
Resulted in taking a couple of big greenies and attempting to dive to the sea floor on the other side of the breakers!

What he didn't realise was that his batteries had broken loose during this attempt to dive [or fly] as he went over the bar.

The loose batteries did only one bit of damage, they destroyed the inboard engine's raw seawater plastic seacock!

Now those onboard did not realize that anything was wrong at first, until the yacht became sluggish and SEEMED to be lower in the water.

Quick action got them back inside the bar, without anymore drama, where MR Camden Haven quickly came to their rescue.

Change the seacock to a bronze ball valve ASAP!

I have a feeling this is a steel yacht. The skin fitting looks like it may be galvanised steel then a short piece of rubber hose to the nylon filled valve. The chances of buying a quality bronze valve these days is not good. The bronze valve would not be any stronger than the nylon filled valve although it may be cheaper. I have a mixture of valves on my yacht, eventually they will all be plastic.

The lid for the strainer should be above the waterline. The water leaking out is possibly just back drain from the engine.